Simlish is a language that was invented for a computer game called "The Sims". It's a made-up language that doesn't actually make sense, but is used by the characters in the game to communicate with each other.
Think of simlish like playing pretend. When you and your friends play pretend, you might make up words or sounds to pretend like you're speaking a different language. That's what the people who made "The Sims" did when they made simlish. They made up some words and sounds that the characters in the game could use to talk to each other in a way that felt like a real language.
When you hear simlish, you might notice that some of the words sound like English words, or even words from other languages. But they're not actually those words - they're just simlish words that sound similar. And if you try to look up a simlish translation online, you probably won't find one, because it's not really a language that people speak outside of "The Sims" game.